An ordinal identifier assigns a numerical value to a test object that indicates its order or location relative to other objects with an otherwise identical description (objects that have the same values for all properties).
You can select 3 types of ordinal identifiers
o Location. Indicates the order in which the object appears within the parent window, frame, or dialog box relative to other objects with an otherwise identical description.
o Index. Indicates the order in which the object appears in the application code relative to other objects with an otherwise identical description.
o Creation Time (Browser objects only). Indicates the order in which the browser was opened relative to other open browsers with an otherwise identical description. This identifier type is only available if more than one Browser object was open when the test object was learned.
[Taken from QTP User Guide]